A. Field
The present invention relates to a drive system for a group of machines each equipped with a drive motor connected by control devices to a DC power source.
B. Related Art
Applying DC power to the drive motor(s) of a machine, for instance a weaving machine, is known. In this procedure AC power is converted by a rectifying unit of the particular machine into DC. This DC is applied by controlled switching units to the weaving machine's drive motor. Said drive motor preferably shall be a switched reluctance motor. Preferably such a weaving machine also contains a capacitive energy buffer connected to the output of the rectifying unit and to the input of the switching units. As a result, the power output beyond the rectifying unit may remain nearly constant even when the power applied to the weaving machine's main drive motor varies. The power applied to said main drive motor of a weaving machine varies according to a periodic motion of said weaving machine because it contains components that are moved in one or the other direction at predetermined times.
The above described drive system meets requirements for weaving. However it is less than desirable for electrically decelerating the weaving machine's main drive motor. For example, the main drive motor must be decelerated to reduce its speed during weaving or to stop it. In such a case the energy buffer must store the energy released by electrically decelerating the main motor. Therefore an energy buffer of high capacity and/or ability to tolerate high voltages will be required.
As regards rapidly operating weaving machines, it is nearly impossible to store the total energy released during deceleration into an energy buffer. Either an energy buffer of very large capacity would be needed, or the energy buffer's voltage would be too high. To preclude excessively high energy buffer voltages, it is known in the state of the art to couple a resistor in parallel with the energy buffer when said buffer's voltage becomes excessively high, whereby energy is removed from said buffer and converted into heat in said resistor. When the main drive motor of a weaving machine must be frequently decelerated, there will be danger that the resistor temperature will become excessive. Moreover the heat dissipated by such a resistor must be absorbed by air-conditioning equipment in the weaving room. This aspect again requires expenditure of relative large amounts of energy.